Resources for augmenting the performance of an individual musician through extemporaneous self-accompaniment have seen continuous development as new technology has become available and economical. As examples, the mechanical accordian, with bass and chord buttons, evolved to the electronic chord organ. In an example of such note-group pattern-generating devices, U.S. Pat. No. 4,366,739 to DeLong et al. discloses a system for playing chords from the pedalboard of an electronic organ. Automated chord formation of this type generally fails to satisfy the artistic needs of advanced musicians who prefer the freedom to express individual styling by structuring chords and note clusters in varied and unusual inversions and voicings.
Electronic organ and music synthesizer development has led to the current availability of functional electronic modules which may be combined as building blocks in musical instrument architecture. The widespread acceptance of MIDI (Musical Instrument Digital Interface) standards has greatly enhanced the interchangeability of such modules and facilitated their integration in interconnected combinations. The evolution of MIDI-based technology has provided unprecedented potential for creating novel synthesized self-accompaniment derived from a lead voice performance: the lead voice notes are encoded in MIDI format to provide Channel Voice messages comprising Note On event messages and Note Off event messages which include channel addressing, pitch (key #) and velocity (attack and release) data. Such messages along with system command messages are transmitted via standardized MIDI cables typically through one or more MIDI processing modules to a sound-generating device comprising a polyphonic tone generator module containing a bank of independent tone generator units addressed and command in real time by MIDI Voice Channel messages as described above.
Synthesizers have been adapted to enable an electric guitar to produce a synthesized sound much different from its natural sound by adapting the guitar to become a controller for a polyphonic tone generator in the synthesizer. On a typical six string guitar, each string is sensed with an individual magnetic pickup, providing six analog outputs, one from each string, which are encoded into MIDI formatted serial note data messages. These are processed and addressed to the tone generator which is programmed to automatically generate tones related in some predetermined manner to the notes played on the guitar. An example of prioritizing a polyphonic tone generator to maximize the utility of a limited number of channels is found in U.S. Pat. No. 4,706,538 to Yoshida.
In a basic mode, the tone generators are made to "pitch-track" the guitar performance: that is to play, for each guitar note played, a synthesized tone having the same pitch, Note On event timing and Note Off event timing as the guitar note but in a much different tonal color or timbre. For further variety, the processing may be programmed to offset the pitch up or down by a designated interval (such as a third, fifth of a chromatic or modal scale, or an octave). A switch usually is provided to enable the musician to bypass the synthesizer and play only amplified natural guitar sound. A more elaborate setup may provide performance of both the natural sound and the synthesized sound simultaneously.
The ability to sustain (and subsequently release) notes has long been recognized as an important resource in playing music. This ability is of particular importance in such instruments as acoustic guitars, where limited sustain effects are available through appropriate interaction of the strings, frets and fingers, and the piano, where the sustain pedal enables foot control to take over some of the sustaining tasks from the fingers. The problem limiting the musical potential of such sustaining capability is well-known: each note present or played with sustain enabled (sustain pedal down) becomes sustained, therefore playing a sequence of notes easily builds up a dissonant group of sustained notes. This problem is less severe if the sustained notes decay rapidly, as with the higher notes of the piano, but becomes more severe with the longer sustain of the acoustic guitar, and becomes especially severe with non-decaying sustained notes of electronic tone generators.
In synthesizers such as the guitar synthesizer described above, it is known to provide the player with capability of sustaining notes by temporarily suspending the normal immediate transmission of Note Off event messages and then sending them at a later time, typically under control of a foot switch, which thus acts in the manner of a piano sustaining pedal. As with the piano, there is no way for the player to sustain only particular non-sequential notes out of a played sequence, or to add new selected notes to a sustained group so as to accumulate a musically desired larger sustained group; therefore in known art the practice of pedal-sustaining is limited to a brief fill-in role since sustained groups must be promptly terminated by releasing the sustain pedal before playing any further passages containing notes not wanted in the sustained group. If the musician wishes to hold a sustained group as background accompaniment while proceeding independently with new lead passages, he must dedicate some of his fingers to the task of holding the sustained group since normal pedal-sustain fails to provide such facility.
It has been discovered in the conception of this invention that the limitations cited above may be overcome by a particular configuration of controlling equipment and manner of practice by a musician, enabling the selection of particular notes of a lead voice sequence for initiating corresponding sustained accompaniment notes, while inhibiting other notes of the lead voice sequence from initiating sustained accompaniment notes, and thus enabling the accumulation of a musically desired stack or voicing of sustained notes, over which the lead voice may be played independently, thus providing the musician with enhanced orchestral-like self-accompaniment capabilities significantly beyond those available in known art. Furthermore it has been found that the practice of the invention is beneficially applicable to other forms of time-extension of accompaniment notes, such as echo and reverberation, as well as sustain.